1995 OPEN FORUM Abstracts
PARTIAL LIQUID VENTILATION: HISTOLOGIC DIFFERENCES BETWEEN HIGH FREQUENCY VENTILATION AND CONVENTIONAL VENTILATION.
Kendra M. Smith,MD, Dennis R. Bing.RRT, Raye-Ann deRegnier, MD, Pat A. Meyers, RRT, Susan C. Simonton, MD, Stephen J. Boros, MD, Mark C. Mammel, MD. Infant Pulmonary Research Center, Children's Health Care - St. Paul.
Partial liquid ventilation (PLV), when compared to conventional ventilation (CV), better preserves lung architecture in animal studies. High frequency ventilation (HFV) causes less alveolar/airway disruption from barotrauma in animals and humans. No studies have investigated lung pathology following PLV/HFV. We hypothesized that PLV would produce less lung damage after prolonged ventilation when compared to CV, and that PLV/HFV would further reduce lung damage. We induced lung injury with saline lavage (PaO2< = 60 torr, FiO2 1.0) in 36 newborn piglets. After stabilization on CV with gas, animals were randomized to one of five groups for 20 hrs: 1) CV with gas ventilation (n=8); 2) PLV with CV (n=7); 3) PLV with jet ventilation, IMV 7 (Bunnell; n=7); 4) PLV with oscillation (SensorMedics 3100; n=7); or 5) PLV with flow interruption, IMV 7 (Infrasonics Infant Star; n=7). Animals in groups 2-5 received preoxygenated perfluorocarbon (LiquiVent ®, Alliance Pharm.Corp.) to Approximate FRC by assessment of ET tube meniscus, which was checked hourly for replacement of evaporative losses. Ventilator support was adjusted to normalize blood gases. Animals remained supine with 20º head elevation. At autopsy, lungs were inflated to 40 cm H20, clamped, then fixed in formalin. Slides from animals surviving >16 hrs (n=29) were scored by a pathologist (SS) blinded to ventilation type. We scored alveolar and interstitial inflammation and hemorrhage, edema, atelectasis, necrosis, and presence of hyaline membranes on a 0-4 scale. Upper (UL) and lower lobes (LL) were scored separately, then summed. Scores were analyzed using the Kruskal-Wallis test. We assessed group differences with the Newman-Keuls test. Total injury scores were significantly lower in all PLV groups compared to CV-gas (p < 0.05). There were no differences in UL scores; LL scores were significantly lower in all PLV groups (p < 0.05). CV-gas produced more alveolar inflammation, edema, atelectasis, and hyaline membrane formation than did any type of PLV (p < 0.001). Conclusion: PLV, with CV or HFV, reduces lung damage after prolonged ventilation. Similar injury scores in UL suggest unequal perfluorocarbon distribution, with greater protection in dependent lung regions. (LiquiVent ®, provided by Alliance Pharm. Corp.)